Перегляд за Автор "Korotin, S."

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  • Ескіз
    Документ
    Systematic investigation of chemical abundances derived using IR spectra obtained with GIANO
    (2019) Caffau, E.; Bonifacio, P.; Oliva, E.; Korotin, S.; Capitanio, L.; Andrievsky, Serhii M.; Collet, R.; Sbordone, L.; Duffau, S.; Sanna, N.; Tozzi, A.; Origlia, L.; Ryde, N.; Ludwig, H.-G.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    ontext. Detailed chemical abundances of Galactic stars are needed in order to improve our knowledge of the formation and evolution of our galaxy, the Milky Way. Aims. We took advantage of the GIANO archive spectra to select a sample of Galactic disc stars in order to derive their chemical inventory and to compare the abundances we derived from these infrared spectra to the chemical pattern derived from optical spectra. Methods. We analysed high-quality spectra of 40 stars observed with GIANO. We derived the stellar parameters from the photometry and the Gaia data-release 2 (DR2) parallax; the chemical abundances were derived with the code MyGIsFOS. For a subsample of stars we compared the chemical pattern derived from the GIANO spectra with the abundances derived from optical spectra. We derived P abundances for all 40 stars, increasing the number of Galactic stars for which phosphorus abundance is known. Results. We could derive abundances of 14 elements, 8 of which are also derived from optical spectra. The comparison of the abun-dances derived from infrared and optical spectra is very good. The chemical pattern of these stars is the one expected for Galactic disc stars and is in agreement with the results from the literature. Conclusions. GIANO is providing the astronomical community with an extremely useful instrument, able to produce spectra with high resolution and a wide wavelength range in the infrared.
  • Ескіз
    Документ
    The CEMP star SDSSJ0222–0313: the first evidence of proton ingestion in very low-metallicity AGB stars?
    (2019) Caffau, E.; Monaco, L.; Bonifacio, P.; Korotin, S.; Andrievsky, Serhii M.; Cristallo, S.; Spite, M.; Spite, F.; Sbordone, L.; François, P.; Cescutti, G.; Salvadori, S.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    Context. Carbon-enhanced metal-poor (CEMP) stars are common objects in the metal-poor regime. The lower the metallicity we look at, the larger the fraction of CEMP stars with respect to metal-poor stars with no enhancement in carbon. The chemical pattern of CEMP stars is diversified, strongly suggesting a different origin of the C enhancement in the different types of CEMP stars. Aims. We selected a CEMP star, SDSS J0222–0313, with a known high carbon abundance and, from a low-resolution analysis, a strong enhancement in neutron-capture elements of the first peak (Sr and Y) and of the second peak (Ba). The peculiarity of this object is a greater overabundance (with respect to iron) of the first s-process peak than the second s-process peak. Methods. We analysed a high-resolution spectrum obtained with the Mike spectrograph at the Clay Magellan 6.5m telescope in order to derive the detailed chemical composition of this star. Results. We confirmed the chemical pattern we expected; we derived abundances for a total of 18 elements and significant upper limits. Conclusions. We conclude that this star is a carbon-enhanced metal-poor star enriched in elements produced by s-process (CEMP-s), whose enhancement in heavy elements is due to mass transfer from the more evolved companion in its asymptotic giant branch (AGB) phase. The abundances imply that the evolved companion had a low main sequence mass and it suggests that it experienced a proton ingestion episode at the beginning of its AGB phase.